Traditional microscope systems are generally unable to measure intermolecular interactions accurately and cost effectively. One type of microscope system is the atomic force microscope (AFM), which has been used to image and/or measure the topography of various surfaces. AFMs, however, suffer from a mechanical instability that prevents the accurate measurement of intermolecular interactions. In particular, AFM's are generally unable to control tip snap-in during tip approach and/or tip snap-off during tip retraction. As a result, AFMs are generally unable to detect intermediate states of various intermolecular interactions such as, for example, the capillary forces between two silicon surfaces.
One limitation in the speed at which an atomic force microscopes may scan a sample is the size of the cantilever. In order to overcome this weakness, typical high-speed atomic force microscopes employ a small cantilever. However, the smaller cantilever of high-speed atomic force microscopes adds complexity to the deflection detection systems, and these systems tend to be limited to between one and ten frames per second.
Another type of microscope system is the interfacial force microscope (IFM). Traditional IFM's use an electrical detection process to measure various surface phenomena. IFM's, however, have not been widely used due to the low sensitivity and technical complexity of their electrical detection process. Thus, traditional microscope systems have generally been unable to measure intermolecular interactions accurately and cost effectively.
AFM has been used to map topographic structures and mechanical properties, such as viscoelastic and adhesional properties using modulation techniques. However, such modulation techniques may be challenging to interpret because of, among other things, a complex dependence on amplitude and phase of driving signals due to the nonlinear nature of tip-sample interaction in the contact regime.